This invention relates generally to building construction, and in particular to constructing tall building frames in a manner that avoids weakening of the building frame and possible collapse of the building in the event of a serious fire.
On Sep. 11, 2001, it is estimated that as many lives were lost from the collapse of the World Trade Center as from the fire and explosion preceding the collapse, including the lives of many New York City police and firefighters. It is also understood that high heat from the blaze raised the temperature of the Trade Center towers"" steel framing close enough to the melting point of steel to bring about catastrophic failure resulting in the building""s collapse.
Tall building frames, comprising a network of interconnected vertical and horizontal structural members often referred to as (vertical) columns and (horizontal) beams, are today protected from high heat if at all merely with conventional static insulation. Unfortunately, such static insulation can only protect the structure for a limited period of time, and certainly does not enable a building to withstand collapse under high heat indefinitely. And, over time, this insulation is prone to wearing off, loss, and deterioration, thereby losing entirely even the limited protection that such insulation provides. For example, a recent article posted at the National Science Foundation""s web site shows a pre-disaster photograph of one of the south tower""s columns, with much of its fireproofing material peeled off. This same article observed that it would be desirable xe2x80x9cto require fireproofing that would enable a skyscraper to withstand complete burnout of its contents without collapsing.xe2x80x9d This is an important goal; the question, of course, is how to achieve this.
Under the conditions which transpired at the World Trade Center on Sep. 11, 2001, passive insulation, such as disclosed in U.S. Pat. Nos. 4,220,685 and 4,723,385, simply will not provide indefinite protection against collapse, but will merely gain a small increase in the time until collapse. The former patent discloses a thin protective foil fastened to the face of a structure to be protected, and under high heat, thermal expansion creates a xe2x80x9cblisterxe2x80x9d which results in an air space which thermally insulates the structure. This benefit would be very short-lived under World Trade Center conditions. The latter patent discloses a phase-conversion material with a water content such that when heated sufficiently, the phase conversion material releases its water content in the form a vapor. This will provide cooling, but only for a very limited time insufficient to avert collapse. U.S. Pat. No. 4,304,082, while not for protection in a fire, similarly to U.S. Pat. No. 4,220,685, also creates an air space to provide insulation.
If one wishes to xe2x80x9cenable a skyscraper to withstand complete burnout of its contents without collapsingxe2x80x9d as set forth above, passive insulation alone will not suffice. Some form of heat exchange (or more precisely, heat removal) system will be required so that heat buildup is removed from the building framing on a continuous basis, indefinitely, until the fire has burned itself out or been extinguished. The heat exchange system itself must be suitably protected and redundant, so that in the event part of that system is physically disabled for example by an explosion such as occurred when the airliners ripped through the Trade Center towers at their initial impact, the remainder of the system will remain operational and compensate for those parts of the system which no longer work.
Heat exchange, of course, is a well established means of cooling or heating as the case may be. Indeed, an entire U.S. patent classification, class 165, has been established strictly for heat exchange. In many instances, heat exchange is used to regulate the temperature of an indoor space so that people inside remain comfortable, such as various forms of heating or air conditioning. Refrigeration, of course, utilizes circulation of a fluid with high specific heat to both cool down the refrigerated space and carry away excess heat from that space.
But, for a situation such as occurred on Sep. 11, 2001, one needs to remove massive amounts of heat, not merely to regulate a temperature within a small temperature zone or refrigerate a limited space. More appropriate to consider as pertinent background, for example, are U.S. Pat. Nos. 3,995,687 and 4,301,320 which relate to cooling of a furnace, or the many patents relating to cooling of the core in a nuclear facility, such as U.S. Pat. Nos. 3,854,524; 3,866,424; 3,935,063; 4,038,134; 4,051,892; 4,560,533; 4,698,201; 5,229,067; 5,319,688; and 5,579,355; as well as disclosure document H119. Also of background interest is U.S. Pat. No. 5,195,575 which appears to be a somewhat general purpose heat tube.
Even in these situations, however, one simply does not encounter the massive scale of a structure such as the World Trade Center Towers with over 100 floors and a huge footprint, or even a much smaller structure of, say ten to sixty floors with perhaps a smaller footprint which still presents a formidable heat exchange challenge. In all these situations, the removal through heat exchange of the massive amounts of heat that would be generated in a situation such as occurred at the World Trade Center is not a trivial undertaking, and the specific solutions to achieve such an objective are not at all apparent or obvious.
A system and related method for protecting a building frame from fire and heat to avoid catastrophic collapse, comprises a plurality of vertical structural members comprising substantially vacant interiors thereof; a plurality of horizontal structural members comprising substantially vacant interiors thereof; a plurality of attachments between ends of the horizontal structural members and side faces of the vertical structural members enabling a coolant to flow between the interiors of the vertical structural members and the interiors of the horizontal structural members; a plurality of coolant pumps for pumping the coolant into the vertical structural members; a plurality of heat release valves for emitting the coolant from the interiors of the vertical structural members and the interiors of the horizontal structural members when a temperature of the coolant reaches a predetermined temperature threshold.